An in-wall sub-woofer with a high volume displacement is disclosed in U.S. Publication No. 2010/0266149 (“the '149 publication”) to Prenta et al. The '149 publication discloses that the speaker system includes at least one pair of active transducers mounted in a wall section. The active transducers may be mounted in at least one enclosure. Each active transducer has a sound radiating surface. Each active transducer is also mounted substantially perpendicular to a surface of the wall section with the sound radiating surfaces substantially parallel to each other. The sound radiating surfaces may be facing each other or away from each other. The in-wall speaker system may also include one or more pairs of passive radiators to generate sound from sound pressure generated by the active transducers. The pairs of speakers in the wall section may be mounted vertically or horizontally within the wall, with a slot or a vent at the opening at the space between the speaker pairs.